Direct-shear tests were conducted on clean glacier ice, several
types of basal ice and frozen substrate material from the
basal zone of the Suess Glacier, Taylor Valley, Antarctica.
Different strain-rates approximating three orders of magnitude
were employed in order to examine whether the rheology of
basal material changes with a change in the rate of strain.
The results of testing indicated that the peak shear-strength
of the materials decreased as slower strain-rates were applied.
High debris-concentration, solid facies and frozen substrate
attained the greatest values of shear-strength. The lowest
values were found in amber ice, which contains a significant
solute concentration and finely dispersed sediment particles.
High solute concentration along with low sediment content
within the ice lattice appears to decrease the shear-strength
of basal ice. Results from this study indicate that preferential
deformation is likely to occur in basal ice above the saturation
point (> 25% ice) and that if frozen substrate and solid debris
facies deform, it is likely to be at a much slower rate than
Sirota, P. 1999. The Structure and Strength of Basal Ice
in the Suess Glacier, Antarctica. Unpublished BSc (hons) dissertation,
in Geography, at the University of Otago, Dunedin, New Zealand.